Method of treating and purifying motor fuels



A sion internal combustion engines.

Patented Dec. 10, 1935 ATENT OFFICE METHOD OF TREATING AND PURIFYING MOTOR FUELS William M. Stratford, New York, N. Y., assignor to The Texas Company, New York, N. Y., a. corporation of Delaware No Drawing. Application January 25, 1932, Serial No. 588,823

Claims.

This invention relates to the treatment of hydrocarbon distillates such, for example, as cracked petroleum naphtha and like motor fuels. More particularly, the invention relates to a method of treating and purifying oils such as petroleum naphthas and the like by extraction with a material comprising furfural, whereby gumforming and other undesirable constituents are separated from the oil and the treated oil rendered stable and more desirable in character.

Ordinarily the lighter distillate hydrocarbons, such for example as petroleum naphtha, having a boiling range suitable for motor fuel, contain undesirable constituents such as sulfur compounds and materials which tend to form gummy deposits in the distillates over a period of time. This is particularly true of distillates such as cracked naphtha derived from the pyrogenic decomposition of petroleum by the well-known cracking processes in general use today.

The ordinary method of refining such distillate oils to reduce the content of undesirable sulfur compounds and gum-forming constituents includes treatment with strong sulfuric acid and alkali, followed by treatment with sodium plumbite solution (the so-called doctor solution) and redistillation. Such ordinary methods of treatment have certain disadvantages, including the cost of chemicals and of the redistillation of the treated oil. One of the more important disadvantages resulting from such treatment is the loss of desirable constituents from the oil, the presence of which render the oil resistant to the well-known knocking phenomena observed in high compres- This resistance to knocking, or the anti-knoc value of the fuel as it is referred to in the current literature, is at the present time expressed in units representing the octane number of the oil. The basis of this representation is so well known as to require no explanation here. It is suihcient to state that the ordinary acid and alkali treatment, followed by distillation, applied to a naphtha of high octane number, particularly naphthas produced by cracking at the higher temperatures, results in a material lowering of the octane number of the oil, with corresponding lowering of its quality.

In the practice of the present invention, which involves the extraction of undesirable sulfur compounds and gum-forming constituents from oil such as cracked naphtha by material comprising furfural, the disadvantages of the ordinary acid, alkali and distillation treatment may be substantially avoided, and the purified motor fuel may be produced at a materially lower cost of treatment without substantial reduction in the octane number of the fuel.

In the practice of the invention the procedure includes the intimate mixing and agitation of 5 the oil or naphtha to be purified with a material comprising furfural. Preferably this material will be a mixture of furfural and water, the exact composition of which may be varied to produce a graduated selective action upon the oil undergoing treatment. For example, the oil may be agitated with an equal quantity of ordinary commercial furfural saturated with water, which is a composition containing about 94% furfural and about 6% of water. Such treatment when carried out at ordinary room temperature of about 70 80 F., results in the extraction of approximately 10% by volume from naphtha derived from an ordinary commercial type of cracking process, such for example as the well-known 2O Holmes-Manley process. The resulting naphtha, when washed free from traces of furfural, is materially improved in that constituents tending to form gum are substantially reduced, as well as is the sulfur content of the oil.

The selective action of the furfural reagent in extracting certain constituents from the oil may be varied, both by a variation in the concentration of furfural used, and by a variation in the temperature of treatment.

Thus, while a particular concentration of 94% furfural and 6% water has been described as applied at a temperature of about '70-80 F., the concentration of water in the reagent may be increased, which will bring about a corresponding lesser degree of extraction from the oil undergoing treatment. On the other hand, using a fixed concentration of a furfural-water mixture, the degree of extraction from the oil may be varied by varying the temperature under which the 40 extraction takes place. Thus, the quantity of extract from the oil undergoing treatment will increase with an increase in temperature, and decrease with a decrease in temperature, depending upon the individual characteristics of the oil undergoing treatment. Extraction temperatures as low as 0 F. may be found desirable, and as high as 200 F. or more. In the latter case, that is, where higher temperatures are used, it is desirable to carry on the extraction under superatmospheric pressure to prevent evaporation of the oil and reagent during the treatment.

The quantity of furfural or reagent comprising furfural which is used in the extracting treatlnfihll may be varied in accordance with the individual characteristics of the oil undergoing treatment. For example, in the case of some types of oils it may be preferable to extract the oil with a comparatively large volume, say several hundred per cent, of 94% furfural at ordinary temperatures, while in the case of other oils it may be desirable to extract with a comparatively small volume, say less than an equal volume of a more concentrated furfural reagent at temperatures well above normal atmospheric temperature.

Although furfural and mixtures of furfural with comparatively small quantities of water have been mentioned specifically as suitable extracting reagents, other mixtures may be found effective,

particularly when applied to oils of unusual characteristics. For example mixtures of furfural with other polar substances, such as alcohol and the like, in varying proportions are found to have a selective solvent action to a different degree upon undesirable constituents of certain oils.

Under ordinary conditions the extraction *treatment with a reagent comprising furfural which is described herein may be applied to a raw distillate oil to produce a finished merchantable product. However, in the case of oils of exceedingly high sulfur content or unusual characteristics as regards tendency to form gum, it may be found desirable to supplement the furfural treatment by the usual acid, alkali and doctor treatment applied either before or after the furfural treatment. Also in many cases it may be found desirable to treat the oil, after extraction with the furfural reagent, with a solution of sodium plumbite.

The material extracted from the oil by the furfural reagent may, after separation of the furfural reagent, be subjected to refining treatment as for example distillation, acid treatment, or treatment to eifect desulfurization, and may thereafter be used for various purposes. If sufiiciently refined it may be blended with the purified motor fuel from which it was originally separated.

Although the extraction treatment with a ma terial comprising furfural has been discussed particularly in connection with the treatment of oils such as cracked petroleum naphthas and the like, the method of treatment is also applicable to other types'of oils, such for example as straightrun naphthas from crude oils of asphaltic characteristics and those having particularly high sulfur content, also shale oils and the like.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method of treating and purifying cracked petroleum naphtha for the production of motor fuel comprising extracting the naphtha with a material comprising a mixture of furfural and water in proportions to each other and to the naphtha. adapted to remove around 10% by volume of the original naphtha as an extract con taining gum-forming constituents and undesirable sulphur bodies without substantial impairment of the anti-knock value of the naphtha.

2. The method of treating and purifying cracked petroleum naphtha for the production of motor fuel comprising extracting the naphtha with a mixture comprising furfural saturated with water at a temperature of about 70 F. to 80 F. and adapted at such temperatures to separate from the naphtha around 10% by volume as an extract whereby gum-forming constituents and undesirable sulphur bodies are removed without substantial impairment of the anti-knock value of the naphtha.

3. The method of treating and purifying petroleum naphtha for the production of motor fuel which comprises mixing with the naphtha a solvent comprising a mixture of furfural substantially saturated with Water at around 70 F. to 80 F. and adapted at such temperatures to separate from a light distillate of the character of cracked naphtha around 10% by volume of material including gum forming constituents as an extract soluble in the solvent mixture, maintaining the mixture under suitable conditions of temperature to effect separation of the naphtha into a fraction substantially insoluble in the solvent and comprising the desired motor fuel product and a fraction soluble in the solvent and containing the undesired extracted constituents, and removing the separated extracted constituents from the solvent treated naphtha.

4. The method of treating and purifying petroleum naphtha for the production of motor fuel which comprises mixing with the naphtha a solvent comprising a mixture of furfural and water and adapted at temperatures of around 70 F. to 80 F. to separate from a light distillate of the character of cracked naphtha around 10% by volume of material including gum forming constituents as an extract soluble in the solvent mixture, maintaining the mixture at a temperature within the range of F. to around 200 F. to effect separation of the naphtha into a fraction substantially insoluble in the solvent and comprising the desired motor fuel product and a fraction soluble in the solvent and containing the undesired extracted constituents, and removing the separated extracted constituents from the solvent treated naphtha.

5. The method of treating and purifying cracked petroleum naphtha for the production of motor fuel, comprisingextracting the naphtha with a solvent comprising furfural in admixture with a polar substance containing a hydroxyl group and of the character of Water and alcohol, in proportion to the furfural and to the naphtha adapted to remove around by volume of the original naphtha as an extract containing gum forming constituents and undesirable sulphur bodies without substantial impairment of the anti-knock value of the naphtha.

WILLIAM M. STRATFORD. 

